Method of making iron cores



June 6, 1950 H. E. OLES 2,510,598

METHOD OF MAKING IRON CORES Filed Dec. 12, 1944 ll llllllllllll lllllllllllllllll lmmll llllllm imllllllll" mmmm I ii a IN VEN TOR. ll ererfE 0/ 5 WGWL 47 F ORA E Y rmma Juno 6, 1950 2,510,598

UNITED STATES PATENT OFFICE METHOD OF MAKING IRON CORES Herbert E. Olea,Indianapolis, Ind., assignor to P. B. Mallory a 00., Inc., Indianapolis,Ind., a corporation of Delaware Application December 12, 1944, SerialNo. 567,850

Claims.

The present invention relates to the art of forming ferromagnetic coremembers, and, mor particularly, to a novel method of making iron coresfrom fine-gauge ferromagnetic wire, and to the products of such method.

It is already known to produce a flexible fabric or web including warstrands of textile material and weft strands of a suitable paramagneticmaierial, such as for exampl iron wire of appropriate thickness. Thisfabric or web was wound up into a core body of appropriate shape,characterized by the presence of a large number of parallel-spaced fineferromagnetic strands.

Cores provided in accordance with this method 4 th present inventionwill become apparent from the following description, taken inconjunction with the accompanying drawing, in. which:

Fig. 1 illustrates the weaving pattern of a ferromagnetic fabricembodying the present invention; the thickness of the several strandsand the spacing thereof being greatly exaggerated for rea sons ofclarity;

Fig. 2 depicts a section taken on line 2-2 of Fig.

Fig. 3 shows a ferromagnetic core of cylindrical shape wound up from thefabric of the invention;

Fig. 4 is a diagrammatic view showing the treatment of the wound corebody by means of a suithad the advantage of low eddy current losses butis able solvent bath; were otherwise not particularly eiilcient in viewFig. 5 is a similar view illustrating the conof their relatively low"space factor." solidating step in the method of the invention in- It isone of the principal objects of the present cluding the application ofpressure with or withlnvention to improve the iron cores of the deoutthe simultaneous application of heat to the scribed generic type andparticularly to increase go preformed core body; and the space factor"thereof, that is, to increase Fig. 6 is a perspective view of thefinished core. the proportion of the core volume occupied by the While apreferred embodiment of the invention ferromagnetic wire to the totalvolume of the core. is described herein, it is contemplated that con- Itis another object of the present invention to siderable variation may bemade in the method of provide a novel type of flexible fabricconstituted procedure and the construction of parts without of warpstrands of electrically insulating diamagdeparting from the spirit ofthe invention. In netic material and of weft strands of ferromagthefollowing description and in the claims, parts netic material, the saidwarp strands being soluble will be identified by specific names forconvenina suitable solvent so that upon winding up the ience, but theyare intended to be as generic in fabric into a core structure, the warpstrands may their application to similar parts as the art will bedissolved and the remaining body compressed permit. and consolidatedthereby to increase the space Referring now more particularly to Figs. 1and 2 factor of the finished product. of the drawing, referencecharacter It denotes It is a further object of the invention to providethe warp threads or strands, while reference a novel and improved methodof forming iron character ll denotes the weft thread or strand. cores inwhich warp strands of an electrically The warp strands may be of anysuitable insulating thermoplastic diamagnetic material are electricallynon-conductive diamagnetic macombined by weaving with weft strands of aparaterial, such as for example conjugated polymagnetic material toconstitute a fabric subsemers, cellulosic materials as natural andrequently wound up on a core, the wound core strucgenerated celluloseand ester and others thereof, ture being subjected to heat and pressureto cause synthetic resins, elastomers, and the like, which thethermoplastic diamagnetic material to flow, are either soluble in asuitable solvent or which whereby the core structure is consolidated andare thermoplastic or fusible in character. The the space factor thereofis increased. weft strand or strands may be of any suitable Theinvention also contemplates a novel type p netic ma ri l ch as. f r pl nof core structure comprising a bundle of substanwire of appropriatethickness, generally less than tially parallel-spaced iron wires ofgreatly re- 0.01 inch in diameter, and is preferably covered duceddiameter bonded together by means of or coated with one or more suitableelectrically thermoplastic diamagnetic materials which is insulatingcompounds or materials including insimple in construction, has excellentphysical sulating varnishes, lacquers, natural and synproperties, suchas high space factor and low thetic resins, elastomers, cellulosicmaterials, and eddy current losses, and which may be readiLv the like.Of course, itis desirable to so select the manufactured on a quantityproduction scale at said covering or coating materials for the paraa lowcost. magnetic strands that they are not attacked by Other and furtherobjects and advantages of the solvent of the warp strands or, ifthermoplasno, a tic and fusible warp strands are employed, that the saidcoating materials have a higher temperaaccordance with the specificapplication which is contemplated. The diamagnetic strands extendlongitudinally of the web, while the paramagnetic strand will extendtransversely of the web, re versing its direction at alternate edges ofthe web to constitute selvedge l2, so formed as to prevent raveling.

The ferromagnetic web embodying the inVen-' tion may be produced bymeans of conventional weaving procedures and may be stored and shippedin such condition, if desired. The iron cores may be formed from thesaid web in various ways. For example, the ferromagnetic web may bewound up to constitute a cylindrical or rodlilse core body it, having aslightly larger diameter than the desired core, as this is shown in Fig.3.

This wound body is now further treated in order to substantiallyeliminate the warp strands and thereby to increase the space factor. Incase the warp strands are soluble in a suitable solvent, the wound corebody is introduced into a treating tank it having a quantity of thesolvent i therein so that the core body is fully submerged in thesolvent (Fig.4). After allowing the solvent to act upon the core bodyfor a sufiicient length of time, most of the warp strands will bedissolved or at least considerably softened. The core body is nowremoved from the solution and is inserted between suitably formedpressure jaws l6 and H (Fig. 5). By pressing the said jaws or pressuredies together, the remaining portion of the dissolved or softened warpstrands will be squeezed out and only the ferromagnetic Weft strandswill remain in a strongly consolidated and condensed position. At thesame time, the

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dimensions of the core bodywill be reduced to those of the desired core.While most of the material of the warp strands will be removed, a smallresidual amount thereof will be instrumental in permanently bonding thewound structure and will prevent unwinding thereof. It has been foundthat the finished core structure has excellent magnetic properties, loweddy current losses, and a very high space factor.

As an alternative of the method of the invention, when the warp strandsare constituted of a thermoplastic or fusible'material, the solventapplying step may be omitted and heat and pressure may be simultaneouslyapplied to the wound core structure by means of the apparatus shown inFig. 5. In this case, jaws l6 and ll are heated, for example by means ofan electric heating element (not shown), to a temperature sufficient tocause fusion or at least softening of the thermoplastic material of thewarp strands. The simultaneous application of heat and. pressure willcause the warp strands to soften and to flow so that their major portionwill bev squeezed out of the wound core body, while their remainingportion upon cooling will permanently bond the weft strand or strandsinto an integral body of reduced dimensions. The core structure obtainedin this manner is shown in Fig. 6 and is likewise characterized by loweddy current losses and a high space factor.

It will be noted that the principles of the invention provide variousimportant advantages.

Of these the most important is that iron cores of a great variety ofshapes and sizes may be readily built up from ferromagnetic wire of verysmall diameter, without the difficulties heretofore encountered inbuilding up cores from fine wire by means of bundling, and the likeprocedures.

It is also to be observed that the cores embodying the inventionsubstantially eliminate the diamagnetic strands from the finished corestruc ture so that the warp strands do not detrimentally affect thespace factor of the finished core.

Moreover, the methods of the invention are very simple and may bereadily applied to the quantity production of iron cores from fine-gaugeiron wire without requiring any expensive or complicated specialequipment.

Although the present invention has been disclosed in connection with afew preferred embodiments thereof, variations and modifications may beresorted to by those skilled in the art without departing from theprinciples of the present invention. Thus, cores having other than asolid cylindrical shape may be made by substantially the same method,such as tubular cores, and o, I or H-shaped cores. In some cases it maybe found advantageous to reverse the relative position of thediamagnetic and paramagnetic strands and to make the warp strands ofparamagnetic material and the weft strand of diamagnetic ma terial. Allthese variations and modifications are considered to be within the truespirit and scope of the present invention, as disclosed in the foregoingdescription and defined by the appended claims.

What is claimed is:

1. The method of forming core structures for electromagnetic deviceswhich comprises provid ing a web with warp strands of relativelyelectrically-non-conductive diamagnetic material and weft strands of awire of ferrous material, winding up a predetermined length of said webto constitute a core, subjecting said core to a solvent treatment tobring the warp strands at least into a semi-fluid state, andsubsequently applying pressure to said core to eliminate the majorportion of the material of the warp strands and to obtain a compactedstructure substantially consisting of closelyspaced ferrous weft strandsbonded together by the remainder of the material of said warp strands.

2. The method of forming core structures for electromagnetic deviceswhich comprises providing a web with warp strands of a diamagnetiodielectric material and weft strands of a wire of ferrous materialcovered by a thin electrically insulating layer, rolling up apredetermined length of said web to constitute abody slightly larger indiameter than that of the desired core,

subjecting the said body to a solvent treatment adapted to convert thewarp strands at least into a semi-fluid state without substantiallyattacking the insulating layer of the weft strands, and

applying pressure to said body to eliminate the said core with a solventto dissolve and to remove at least the major portion of the material ofthe warp strands therein,- and subsequently applying pressure to saidsubstantially eliminate air spaces therefrom and to obtain a dense corestructure consisting of closely spaced ferrous weft strands bondedtogether by the remainder of the material of said warp strands.

4. The method of forming core structures for electromagnetic deviceswhich comprises providing a web with warp of a diamagnetic materialsoluble in a "suitable solvent and weft strands of a ferrous materialcoated with an electrical insulating material, rolling up apredetermined length of said web to constitute a bodylargerindiameterthanthat ofthedesiredcore, treating said body with aliquid which is a solvent for the said warp strands and substantially anon-solvent for the coating of the said weft strands, and subsequentlycompressing the said body to squeeze outthe major portion of thematerial of the warp strands to provide a core structure of the desireddimensions character- 8 iaed by a high space factor and low eddy currentlow, said core structure consisting of closely spaced ferrous weftstrands electrically insulated from each other by coatings of saidinsulating material and bonded together by the remainder of the materialof said warp strands.

HERBERT E. OLES.

REFERENCES CITED The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS

1. THE METHOD OF FORMING CORE STRUCTURES FOR ELECTROMAGNETIC DEVICESWHICH COMPRISES PROVIDING A WEB WITH WARP STRANDS OF RELATIVELYELECTRICALLY-NON-CONDUCTIVE DIAMAGNETIC MATERIAL AND WEFT STRANDS OF AWIRE OF FERROUS MATERIAL, WINDING UP A PREDETERMINED LENGTH OF SAID WEBTO CONSTITUTE A CORE, SUBJECTING SAID CORE TO A SOLVENT TREATMENT TOBRING THE WARP STRANDS AT LEAST INTO A SEMI-FLUID STATE, ANDSUBSEQUENTLY APPLYING PRESSURE TO SAID CORE TO ELIMINATE THE MAJORPORTION OF THE MATERIAL OF THE WARP STRANDS AND TO OBTAIN A COMPACTEDSTRUCTURE SUBSTANTIALLY CONSISTING OF CLOSELY SPACED FERROUS WEFTSTRANDS BONDED TOGETHER BY THE REMAINDER OF THE MATERIAL OF SAID WARPSTRANDS.